This proposal is to seek monies to purchase an Agilent Technologies 5973 GC/MS instrument capable of ionization by electron impact (EI) and positive and negative chemical ionization (CI). Children's Hospital Oakland Research Institute has had long experience in the use of mass spectrometers, particularly GC/MS instruments for clinical and biological studies. These instruments have been essential to the research of three groups, the steroid studies of Dr Cedric Shackleton, research into aging conducted by Dr Bruce Ames and membrane lipid research of Dr Frans Kuypers. The instruments currently being used by these groups are old and in need of replacement, and planning for purchase of a new one is vital if we want to ensure continuity of funded research. A catastrophic failure, not cost-effective to repair, would be a serious problem. Shackleton's group conducts multiple collaborative projects mainly involving steroid identification and measurement. EI GC/MS is the dominant requirement. The most important project is the measurement of analytes for prenatal detection of Smith-Lemli-Opitz syndrome for a national study with Dr James Haddow of the Foundation for Blood Research as PI. In this study, novel steroids discovered for the first time at CHORI using GC/MS, are being measured in a cohort of about 3000 pregnant women deemed to be at higher risk of having an affected fetus. Many other steroid projects are ongoing with NIH funded investigators, for example, studies of endocrine hypertension, childhood androgen disorders, aromatization intermediates, putative new estrogens and prenatal diagnosis of low-estriol disorders. The Ames group have ongoing projects requiring the use of negative CI GC/MS to quantify markers of lipid damage by reactive oxidants (e.g., malondialdehyde) and markers of DNA damage (incorporation of uracil). Dr Kuypers has several projects on the red cell membrane, which require profiling of fatty acids using EI GC/MS. [unreadable] [unreadable]